1. Technical Field of the Invention
The present invention relates to the introduction or modification of service applications within a telecommunications service node.
2. Description of Related Art
In stand-alone or batch computer processing systems, introducing or modifying software (such as is experienced with a version change) presents relatively few difficulties and obstacles. Any applications currently being executed by the supporting computing systems are first terminated, and then the new software application (comprising, perhaps, a new version of an existing application) is loaded onto the system. The necessary applications for system operation are then restarted, and all future data processing operations may be performed using the newly introduced application.
The introduction or modification operation becomes much more problematic in connection with computer processing systems where necessary system operation related applications cannot be terminated for the period of time required for completion of the software introduction or modification. Take, for example, modern stored program control (SPC) telecommunications switches or service nodes like mobile switching centers (MSCs), exchanges, home location registers (HLRs) or service control points (SCPs). Ideally, these types of computer processing systems run perpetually without interruption because of the continuous need for providing communications services to users. More specifically, there is a continuous flow of communications traffic (i.e., calls) being processed through the system, even at off hours of the day and night. Disruptions in service handling, such as would occur if the system were taken off-line in connection with a software introduction or modification, cannot therefore be tolerated.
Call handling service within a telecommunications stored program control node is provided by a number of separately developed service applications. In this regard, a "service" in this context refers to any one of a number of supported operations ranging from a handler for responding to a certain received message (such as a mobile application part (MAP) message handler) to a subscriber based service (such as a flexible call forwarding service). Although each of these "services" is developed separately, all portions that inter-operate must be linked for execution. Linking involves the combination of the various programs for the needed services into a composite program. Linking can, in theory, be accomplished at a number of different times including both before and after loading, and both before and at execution.
Typically, with respect to prior art SPC telecommunications nodes, service programs are linked at the same time they are compiled. These services are thus referred to as being "compile time linked." When a given service for the telecommunications node is subsequently newly introduced or modified, all of the inter-operable service applications must be recompiled and relinked, with the resulting recompiled software substituted (i.e., swapped) for the existing software while call handling service continues, in an uninterrupted fashion, to be provided.
One known mechanism for transitioning during run-time execution between an old compiled software and a new recompiled software loads both versions of the software onto the system and then functions to redirect traffic from the old software to the new software in a gradual manner (perhaps starting with test traffic). Transactions begun with an application or service of the old software are allowed to process to completion using that old software. Transactions begun after loading of the new software are processed by the new software. When the operator is satisfied with new software operation, and all the old software handled transactions are completed, the old software is removed.
To obviate the need for completely recompiling and relinking the software, as well as obviate the need to swap old and new versions of the compiled and linked entire set of software modules during run time execution, the prior art further suggests delaying linking of block programs in SPC telecommunications nodes such that linking is performed in a dynamic fashion at the time of block execution. Software addresses within a modular software system are dynamically linked as the individual software modules are executed. Thus, binding of variables and signals within the software is delayed until such time, during execution, when a given module is actually executed.